Crystalline metallophosphates

ABSTRACT

Microporous crystalline metallophosphate composition having an essential framework structure whose chemical composition in the as synthesised form expressed in terms of mole rations of oxides is: mR(M x  Al y  P z )O 2  where M is silicon, x+y+z=1, m may have a value from 0.02 to 0.3, R is at least one templating agent, x, y and z represent the mole fractions of silicon, aluminium and phosphorous presentin the product, and where x may have a value from 0 to 0.5, y may have a value from 0.25 to 0.5 and z may have a value from 0.25 to 0.5, and where one reactive form of fluoride may be present in an effective amount to form the product, and having a characteristic X-ray powder diffraction pattern containing at least the d-spacings as set forth in Table 1.

The present invention relates in general to a crystallinemetallophosphates, and more particularly to crystallinealuminophosphates and silicoaluminophosphates of the molecular sievetype with a novel structure and the method for its preparation.

Microporous crystalline aluminophosphate compositions having openframework structures formed of AlO₂ and PO₂ tetrahedral units joined bythe sharing of the comer oxygen atoms and characterised by having poreopenings of uniform dimensions have heretofore been disclosed in anumber of publications. U.S. Pat. No. 4,310,440 describesaluminophosphates which constitute a generic class of non-zeolitemolecular sieve materials being capable of undergoing complete andreversible dehydration while retaining the same essential frameworktopology in both the anhydrous and hydrated state.

Microporous crystalline silicoaluminophosphate compositions having openframework structures formed of AlO₂, PO₂ and SiO₂ tetrahedral unitsjoined by sharing of corner oxygen atoms and characterised by havingpore openings of uniform dimension is earlier disclosed for example inU.S. Pat. No. 4,440,871. These products have a chemical composition on awater-free basis as follows:

    mR:(Si.sub.x Al.sub.y P.sub.z)O.sub.2

where "R" represents at least one organic template material which ispresent in the intracrystalline pore system; "m" is the number of molesof "R" present per mole of (Si_(x) Al_(y) P_(z))O₂ and m has a valuebetween 0 and 0.3, the maximum value in each case being dependent on themolecular dimensions of the template material and the available porevolume in the silico-alumino-phosphate structure in question; "x", "y"and "z" are molar fractions of silicon, aluminium and phosphorusrespectively, present as tetrahedral oxides. The minimum value of "x","y" and "z" is 0.01, and the maximum value of "x" is 0.98, of "y" 0.6and of "z" 0.52. The minimum value of "m" in the formula above is 0.02.

Also the silicoaluminophosphates constitute a generic class ofnon-zeolite molecular sieve materials being capable of undergoingcomplete and reversible dehydration while retaining the same essentialframework topology in both the anhydrous and hydrated state.

By the term "essential framework topology" or "essential frameworkstructure" as used in the aforesaid patents, and also in the presentspecification and claims, is meant the spatial arrangement of theprimary Al--O, Si--O and P--O bond linkages.

From U.S. Pat. No. 5,370,851 there is also knownsilico-alumino-phosphate molecular sieves of the same composition, butwith different X-ray diffraction pattern. Chlorides are used in thesynthesis.

WO93/13013 describes synthesis of silico-alumino-phosphates withimproved stability to activation and with a controlled silicon content.Hydrochloric acid is used in the synthesis.

Other microporous aluminophosphates which undergo structurerearrangements, either reversibly or irreversibly, upon partial orcomplete dehydration are also known, for example the minerals varisciteand metavaricite and certain of the synthetic metastablealuminophosphates reported by F. D'Yvoire [Bull.Soc.Chim. France, 1762(1961)].

Synthesis of microporous crystalline silicoaluminophosphates where thereaction mixture is modified with fluoride ions, is earlier describedfor example in U.S. Pat. No. 4,786,487.

The present invention concerns a novel microporous crystallinemetalloophosphate composition, and the method for its preparation.

The microporous crystalline metallophosphate composition has anessential framework structure whose chemical composition in the assynthesised form expressed in terms of mole ratios of oxides is:

    mR(M.sub.x Al.sub.y P.sub.z)O.sub.2

where M is silicon, x+y+z=1, m may have a value from 0.02 to 0.3, R isat least one templating agent, x, y and z represent the mole fractionsof silicon, aluminium and phosphorous present in the product, and wherex may have a value from 0 to 0.5, y may have a value from 0.25 to 0.5and z may have a value from 0.25 to 0.5, and where one reactive form offluoride may be present in an effective amount to form the product, andhaving a characteristic X-ray powder diffraction pattern containing atleast the d-spacings as set forth hereinafter in Table I.

The product can have a chemical composition, expressed in terms of moleratios of oxides, (taken from Example 1):

    0.17 SiO.sub.2 :Al.sub.2 O.sub.3 :0.81 P.sub.2 O.sub.5

and exhibits and X-ray powder diffraction pattern, in its as synthesisedform, which contains at least the d-spacings set forth in Table I setforth hereinafter. The chemical composition can be altered from the onementioned above, by for instance altering the chemical composition ofthe reaction mixture.

The metallophosphate can be prepared by hydrothermal crystallisationfrom a reaction mixture prepared by combining reactive sources ofphosphorus, silicon and aluminium with water and fluoride and at leastone structure directing agent (template) which can include organicamines and quartenary ammonium compounds, and most preferablytetramethylammonium hydroxide. In the as-synthesized form, wherein theproduct prepared by hydrothermal crystallisation has not been subjectedto a post-synthesis treatment effective in removing the structuredirecting agent, this agent is contained within the framework structureof the metallophosphate in the amounts which vary per mole of Al₂ O₃.The structure directing agent is readily removed by calcination and doesnot appear to be an essential constituent of the product.

The novel microporous metallophosphate of the present invention can beproduced by hydrothermal crystallisation from a reacting mixturecontaining reactive sources of phosphorous, silicon, fluorine andaluminium and a organic templating agent, preferably tetramethylammoniumhydroxide. The preparative process typically comprises forming areaction mixture which in terms of molar ratios of oxides is

    0-4 SiO.sub.2 :Al.sub.2 O.sub.3 :0.5-6 P.sub.2 O.sub.3 :7-300 H.sub.2 O

and contains at least one organic templating agent and one reactive formof fluorine in an effective amount which forms the product.Representative of the amount of organic template employed herein is anamount between 0.5 and about 5 moles of organic templating agent, and0.01 to 3 moles of HF per mole of Al₂ O₃. The reaction mixture is placedin a reaction vessel inert towards the reaction mixture and heated to atemperature of at least about 70° C., preferably between 75° C. and 200°C., until crystallised, usually for a period from 2 hours to 3 weeks ormore. The solid crystalline reaction product is then recovered by anyconvenient method, such as filtration or centrifugation, washed withwater and dried in air at a temperature between ambient and about 110°C.

In a preferred crystallisation method, a solution is prepared fromhydrated alumina, aqueous solution of phosphoric acid, colloidal silica,hydrofluoric acid, and an organic templating agent and is then heated toabout 150° C. from 1 day to 2 weeks. The preferred ratio of inorganicoxides in the initial solution is:

    0.05-0.5 SiO.sub.2 :Al.sub.2 O.sub.3 :0.5-4 P.sub.2 O.sub.5 :20-200 H.sub.2 O

The preferred initial solution contains between 0.5 and 2.5 moles oforganic templating agent and 0.1 to 2 moles of HF per mole of Al₂ O₃.

The material of present invention can alternatively be crystallised froma gel formed from an organic templating agent and appropriatephosphorous, silicon, fluorine and aluminium sources such as phosphoricacid, Ludox LS, hydrofluoric acid and pseudo-boehmite hydrated aluminiumoxide, and digested via conditions typical of those detailed in U.S.Pat. No. 4,440,871.

Not all templating agents suitably employed in preparation of allsilicoaluminophosphates are believed to be generally suitable for thepreparation of the product. The use of tetramethylammonium hydroxide hasbeen found to act as an acceptable templating agent for use in thepreparation.

The as-synthesized compositions are isolated after synthesis andadvantageously washed with water. The as-synthesized compositions maycontain the organic templating agent within the intracrystalline poresystem. The form of the organic templating agent may be an occludedmolecular species (or may be present as a charge balancing cation). Thefluoride may also be present in the structure and may be engaged inmutual interaction with the template or with the framework as astabilising unit, it may also be present as a occluded species. Ingeneral, it is desirable to remove the organic templating agent by forexample calcination at a temperature sufficient to remove substantiallyall of the organic templating agent. The calcination temperature isgenerally between 300° C. and about 700° C., i.e., whereby the organictemplating agent is removed by thermal degradation.

The template-containing as-synthesized form of thesilicoaluminophosphate of the present invention has an essentialframework structure whose chemical composition expressed in terms ofmole ratios of oxides can be (taken from Example 1):

    0.17 SiO.sub.2 :Al.sub.2 O.sub.3 :0.81 P.sub.2 O.sub.5

and has characteristic X-ray powder diffraction pattern which containsat least the d-spacings set forth in Table I below:

                  TABLE I                                                         ______________________________________                                        2 θ     d (Å)                                                                              Relative Intensity                                     ______________________________________                                        10.4-10.7     8.50-8.26                                                                              VS                                                       11.3-11.7 7.82-7.56 W                                                         12.0-12.3 7.37-7.19 W                                                         13.2-13.6 6.70-6.51 W                                                         19.6-20.0 4.53-4.44 M                                                         20.7-21.1 4.29-4.21 M                                                         23.0-23.4 3.86-3.80 M                                                         23.6-24.0 3.77-3.70 W                                                         24.4-24.7 3.65-3.60 W                                                         25.4-25.8 3.50-3.45 W                                                         27.1-27.5 3.29-3.24 W                                                       ______________________________________                                    

In some of the X-ray patterns reported, the relative intensities of thed-spacings are indicated by the notations VS, S, M, W and VW whichrepresents Very Strong, Strong, Medium, Weak and Very Weak,respectively.

The above X-ray pattern and all other X-ray patterns appearinghereinafter were obtained by use of either a standard X-ray powderdiffraction technique or by use of computer based techniques using aSiemens D-500 X-ray powder diffractometer. When the standard X-raytechnique is employed the radiation source is a high-intensity, coppertarget, X-ray tube operated at 40 kV and 50 mA. The diffraction patternfrom the copper K-alpha radiation and Germanium monochromator wererecorded by a X-ray spectrometer scintillation counter, pulse heightanalyser and strip chart recorder.

Flat compressed powder samples are scanned at 1 degrees (2θ) per minute.Interplanar spacings (d) in the Angstrom units are obtained from theposition of the diffraction peaks as 2θ where theta is the Bragg angle.Intensities were determined from the heights of diffraction peaks aftersubtracting background, "I₀ " being the intensity of the strongest lineor peak, and "I" being the intensity of each of the other peaks.

As will be understood by those skilled in the art, the parameter 2θ,irrespective of the technique employed, is subjected to both human andmechanical error, which in combination, can impose an uncertainty ofabout 0.4° on each reported value of 2 theta. This uncertainty is ofcourse, also manifested in the reported value of the d-spacings, whichare calculated from the 2 theta values. This imprecision is generalthroughout the art and is not sufficient to preclude the differentiationof the present crystalline materials from the compositions of the priorart. The relative intensities and peak positions may vary with thehydration state of the samples, and the content of organic and inorganicmaterial. Further the relative intensities may also vary due to forexample orientational effects of the crystals.

When the as-synthesized compositions are calcined, i.e., heated to atemperature sufficiently high (typically in the 300° C. to 700° C.range) or otherwise treated, such as by chemical oxidation, to removeessentially all of the organic templating agent present in theintracrystalline pore system and are allowed to rehydrate in ambientair, the composition has an X-ray powder diffraction pattern whichcontains at least the d-spacings set forth in Table II below:

                  TABLE II                                                        ______________________________________                                        2 θ     d (Å)                                                                            Relative Intensity                                       ______________________________________                                        10.40         8.50   VS                                                         12.05 7.34 W                                                                  12.49 7.08 W                                                                  13.11 6.75 W                                                                  13.83 6.40 W                                                                  20.83 4.29 M                                                                  24.05 3.69 W                                                                ______________________________________                                    

The product exhibits surface characteristics which make it useful as acatalyst or catalyst support in various hydrocarbon conversion andoxidative combustion processes. The product can be associated withcatalytically active metals, e.g., by framework substitution, byimpregnation, doping and the like, by methods traditionally used in theart for fabrication of catalyst compositions.

Among the hydrocarbon conversion reactions that can be catalysed by thenew composition are cracking, hydrocracking, alkylation for both thearomatic and isoparaffin types, isomerization including xyleneisomerization, polymerisation, reforming, hydrogenation,dehydrogenation, transalkylation, dealkylation, hydrodecyclization anddehydrocyclization.

The results further show that the new compositions have a narrow poredstructure with a pore size of at less than 4 Angstrom, which make themsuitable for use as methanol to olefin catalysts.

The following examples are provided to illustrate the invention and arenot to be construed as limiting thereof:

EXAMPLE 1

a) A reaction mixture was prepared by combining 3.39 grams of apseudo-boehmite phase (73.2 wt. % Al₂ O) and 15.87 grams H₂ O to whichwas added 5.52 grams of 85 wt. % orthophosphoric acid (H₃ PO₄), andstirred until homogeneous. 0.5 grams of Ludox LS (approx. 30 wt. % SiO₂)and 0.53 grams of 48 wt. % hydrofluoric acid (HF) was blended into thismixture. To this mixture was added 4.28 grams of tetramethylammoniumhydroxide pentahydrate (TMA) and stirred until homogeneous. Thecomposition of the final mixture, in terms of molar oxide ratios was:

    1.0 TMA:0.1 SiO.sub.2 :Al.sub.2 O.sub.3 :P.sub.2 O.sub.5 :0.5 HF:50 H.sub.2 O

The reaction mixture (30 grams) was sealed in a Teflon jar and heated inan oven at 150° C. for 21 hours. The solids were recovered bycentrifugation, washed with H₂ O, and dried in air at ambienttemperature.

The 3.7 grams of dried product had an X-ray powder diffraction patternwhich indicated the product with a smaller amount of an impurity phase.The product had an X-ray powder diffraction pattern characterised by thedata in Table A.

                  TABLE A                                                         ______________________________________                                        2 θ       d (Å)                                                                            100 I/Io                                               ______________________________________                                        10.61           8.33   100                                                      11.49 7.69 2                                                                  12.51 7.28 5                                                                  13.46 6.57 8                                                                  14.47 6.11 1                                                                  17.16 5.16 1                                                                  18.07 4.91 1                                                                  19.80 4.48 13                                                                 20.90 4.25 24                                                                 21.88 4.06 1                                                                  23.20 3.83 12                                                                 23.81 3.73 5                                                                  24.59 3.62 10                                                                 25.62 3.47 8                                                                  27.30 3.26 3                                                                  28.21 3.16 1                                                                  29.17 3.06 1                                                                ______________________________________                                    

b) A portion of the product obtained in part a) was calcined in air byheating to 600° C. and holding at 600° C. for 4.5 hours. After coolingto room temperature and rehydrating in ambient air, the calcined solidhad a X-ray powder diffraction pattern characterised by the data in thefollowing table:

                  TABLE B                                                         ______________________________________                                        2 θ       d (Å)                                                                            100 I/I.sub.o                                          ______________________________________                                        10.40           8.49   100                                                      12.05 7.34 2                                                                  12.49 7.08 2                                                                  13.10 6.75 4                                                                  13.83 6.36 4                                                                  14.73 6.01 1                                                                  15.85 5.59 3                                                                  19.57 4.53 4                                                                  20.11 4.41 5                                                                  20.68 4.29 10                                                                 21.86 4.06 5                                                                  22.32 3.98 2                                                                  23.16 3.83 5                                                                  24.05 3.69 10                                                                 24.64 3.61 3                                                                  26.11 3.41 9                                                                  26.92 3.31 3                                                                  27.69 3.22 3                                                                  29.32 3.04 2                                                                ______________________________________                                    

A portion of the 3.7 grams of calcined product was analysed and thefollowing chemical analysis obtained:

    0.17 SiO.sub.2 :Al.sub.2 O.sub.3 :0.81 P.sub.2 O.sub.5

EXAMPLE 2

A reaction mixture was prepared by combining 3.28 grams of apseudo-boehmite phase (73.2 wt. % Al₂ O₃) and 15.45 grams H₂ O to whichwas added 5.49 grams of 85 wt. % orthophosphoric acid (H₃ PO₄), andstirred until homogeneous. 0.52 grams of Ludox LS (approx. 30 wt % SiO₂)and 1.0 grams of 48 wt. % hydrofluoric acid (HF) was blended into thismixture. To this mixture was added 4.33 grams of tetramethylammoniumhydroxide pentahydrate (TMA) and stirred until homogeneous. Thecomposition of the final mixture, in terms of molar oxide ratios was:

    1.0 TMA:Al.sub.2 O.sub.3 :P.sub.2 O.sub.5 :1HF:0.1 SiO.sub.2 :50 H.sub.2 O

The reaction mixture (approx. 30 grams) was sealed in a Teflon jar andheated in an oven at 150° C. for 21 hours. The solids were recovered bycentrifugation, washed with H₂ O, and dried in air at ambienttemperature.

The approx. 3 grams of dried product had an X-ray powder diffractionpattern which indicated UiO-S7 with a smaller amount of an impurityphase. The product had an X-ray powder diffraction pattern characterisedby the data in Table A.

EXAMPLE 3

A fluoride modified aluminophosphate gel containing the organic aminetetramethyl ammonium hydroxide (TMAOH) was prepared. The gel had a molaroxide ratio of

    1 Al.sub.2 O.sub.3 :1 P.sub.2 O.sub.5 :0.2 HF:1 TMAOH:H.sub.2 O

The gel was prepared in teflon liners in which pseudobohemite was firstmixed with water and phosphoric acid. The amine was then added followedby HF after which the gel was well stirred. The liners were put instainless steel autoclaves and heated in an oven at 150° C. for 21hours, after which they were quenched in cold water and themicrocrystalline product separated, washed with water and dried. Theproduct had an X-ray powder diffraction pattern characterised by thedata in Table I.

We claim:
 1. Microporous crystalline metallophosphate composition havingan essential framework structure whose chemical composition in the assynthesised form expressed in terms of mole ratios of oxides is:

    mR(M.sub.x Al.sub.y P.sub.z)O.sub.2

where M is silicon, x+y+z=1, m is from 0.02 to 0.3, R is at least onetemplating agent, x, y and z represent the mole fractions of silicon,aluminium and phosphorous present in the product, and where x is from 0to 0.5, y may have a value from 0.25 to 0.5 and z is from 0.25 to 0.5,and where one reactive form of fluoride may be present in an effectiveamount to form the product, and having a characteristic X-ray powderdiffraction pattern containing at least the d-spacings and relativeintensities as set forth below:

    ______________________________________                                        d (Å)    Relative Intensity                                               ______________________________________                                        8.50-8.26    VS                                                                 7.82-7.56 W                                                                   7.37-7.19 W                                                                   6.70-6.51 W                                                                   4.53-4.44 M                                                                   4.29-4.21 M                                                                   3.86-3.80 M                                                                   3.77-3.70 W                                                                   3.65-3.60 W                                                                   3.50-3.45 W                                                                   3.29-3.24  W.                                                               ______________________________________                                    


2. A calcined silicoaluminophosphate, having a characteristic X-raypowder diffraction pattern comprising at least the d-spacings andrelative intensities as set forth below

    ______________________________________                                               d (Å)                                                                          Relative Intensity                                                ______________________________________                                               8.50 VS                                                                  7.34 W                                                                        7.08 W                                                                        6.75 W                                                                        6.40 W                                                                        4.29 M                                                                        3.69 W                                                                      ______________________________________                                    


3. A calcined silicoaluminophosphate according to claim 2, wherein thechemical compositions in terms of mole ratios of oxides is:

    0.17 SiO.sub.2 :Al.sub.2 O.sub.3 :0.81 P.sub.2 O.sub.5

and having a characteristic X-ray powder diffraction pattern comprisingat least the d-spacings and relative intensities as set forth below:

    ______________________________________                                               d (Å)                                                                          Relative Intensity                                                ______________________________________                                               8.49 100                                                                 7.34 2                                                                        7.08 2                                                                        6.75 4                                                                        6.36 4                                                                        6.01 1                                                                        5.59 3                                                                        4.53 4                                                                        4.41 5                                                                        4.29 10                                                                       4.06 5                                                                        3.98 2                                                                        3.83 5                                                                        3.69 10                                                                       3.61 3                                                                        3.41 9                                                                        3.31 3                                                                        3.22 3                                                                        3.04 2                                                                      ______________________________________                                    


4. Process for preparing a microporous crystallinesilicoaluminophosphate composition according to any one of claims 1-3,wherein a reaction mixture is formed having a composition in terms ofmole ratios of oxides of

    0-4 SiO.sub.2 :Al.sub.2 O.sub.3 :0.5-6 P.sub.2 O.sub.5 :7-300 H.sub.2 O

and containing from 0.5 to about 5 moles of at least one organictemplating agent, and containing from 0.01 to about 3 moles of areactive fluorine source, and heating the reaction mixture thus formedat a temperature of at least 70° C. to about 200° C. under autogenouspressure until crystals of said metallophosphate are formed.
 5. Processaccording to claim 4, wherein a reaction mixture is formed having acomposition in terms of mole ratios of oxides of

    0.05-0.5 SiO.sub.2 :Al.sub.2 O.sub.3 :0.5-4 P.sub.2 O.sub.5 :20-200 H.sub.2 O.


6. Process according to claim 4, wherein tetramethylammonium hydroxideis used as templating agent.
 7. Process according to claim 4, whereinthere is used a gel composition in terms of molar ratios as follows:

    1.0 TMA:0.1 SiO.sub.2 :Al.sub.2 O.sub.3 :P.sub.2 O.sub.5 :0.5 HF:50 H.sub.2 O.


8. 8. A method of producing olefins from methanol comprising contactingmethanol with a catalyst comprising the composition of any one of claims1-3 under conditions effective to form olefins.